The impact of intraocular pressure reduction on retinal ganglion cell function measured using pattern electroretinogram in eyes receiving latanoprost 0.005% versus placebo

Abstract

Purpose: To evaluate the impact of intraocular (IOP) reduction on retinal ganglion cell (RGC) function measured using pattern electroretinogram optimized for glaucoma (PERGLA) in glaucoma suspect and glaucomatous eyes receiving latanoprost 0.005% versus placebo.

Methods: This was a prospective, placebo-controlled, double masked, cross-over clinical trial. One randomly selected eye of each subject meeting eligibility criteria was enrolled. At each visit, subjects underwent five diurnal measurements between 8:00 am and 4:00 pm consisting of Goldmann IOP, and PERGLA measurements. A baseline examination was performed following a 4-week washout period, and repeat examination after randomly receiving latanoprost or placebo for 4-weeks. Subjects were then crossed over to receive the alternative therapy for 4 weeks following a second washout period, and underwent repeat examination. Linear mixed-effect models were used for the analysis.

Results: Sixty-eight eyes (35 glaucoma, 33 glaucoma suspect) of 68 patients (mean age 67.4 ± 10.6 years) were enrolled. The mean IOP (mmHg) after latanoprost 0.005% therapy (14.9 ± 3.8) was significantly lower than baseline (18.8 ± 4.7, p<0.001) or placebo (18.0 ± 4.3), with a mean reduction of -20 ± 13%. Mean PERGLA amplitude (μV) and phase (π-radian) using latanoprost (0.49 ± 0.22 and 1.71 ± 0.22, respectively) were similar (p > 0.05) to baseline (0.49 ± 0.24 and 1.69 ± 0.19) and placebo (0.50 ± 0.24 and 1.72 ± 0.23). No significant (p > 0.05) diurnal variation in PERGLA amplitude was observed at baseline, or using latanoprost or placebo. Treatment with latanoprost, time of day, and IOP were not significantly (p > 0.05) associated with PERGLA amplitude or phase.

Conclusion: Twenty percent IOP reduction using latanoprost monotherapy is not associated with improvement in RGC function measured with PERGLA.

Figure 1

Flowchart illustrates the study design consisting of a screening visit and 3 diurnal examinations that included 5 measurements of intraocular pressure, blood pressure, and pattern electroretinogram testing. A baseline examination was performed following a four-week washout period, and repeat examination after randomly receiving latanoprost 0.005% or placebo for four-weeks. Subjects were then crossed over to receive the alternative therapy for 4 weeks following a second washout period, and underwent repeat examination.

Figure 2

Histogram illustrates the mean intraocular at each of five diurnal time points obtained at the baseline session compared with treatment using latanoprost 0.005% and placebo. The IOP at the latanoprost session was significantly (p < 0.001) lower compared with baseline and placebo at all time-points.

Figure 3

Distribution of pattern electroretinogram amplitude (A) and phase (B) values at the baseline, latanoprost and placebo sessions. The whiskers represent the minimum and maximum values; the ends of the box represent the 25^th and 75^th percentiles and the horizontal line inside the box represents the median at the 50^th percentile value.

Figure 4

Scatter plot of pattern electroretinogram amplitude (A, left) and phase (B, right) values demonstrates similar values at baseline compared with latanoprost 0.005% treatment among the study population of glaucoma suspects (GS) and eyes with perimetric glaucoma (PG).

Figure 5

Scatter plot of pattern electroretinogram (PERGLA) amplitude values illustrates the relationship between change in PERGLA response and change in intraocular pressure after latanoprost 0.005% treatment among the study population of glaucoma suspects (GS) and eyes with perimetric glaucoma (PG).